76 Mr. Faraday on the Limits of Vaporisation. 



therefore appear that nitrate of ammonia is a salt volatile at 

 common temperatures, although it is just possible that slow 

 decomposition may take place in it, and so nitric acid or its 

 elements pass over. 



No. 17. Bottle, solution of persulphate of copper ; tube, 

 crystals of ferro-prussiate of potash. The crystals had 

 attracted most of the water from the cupreous salt ; but the 

 solution of ferro-prussiate and that of the copper had their 

 proper colour ; neither were rendered brown ; no salts had 

 been volatilised. 



No. 18. Bottle, solution of acetate of lead ; tube, iodide of 

 potassium. The acetate of lead is now dry ; the iodide of 

 potassium has taken all the water and formed a brown solution, 

 in which there is free iodine ; probably a little acetic acid has 

 passed over and caused the change in the iodide of potassium. 

 There is no appearance of iodide of lead in the tube, but there 

 is in the bottle, and most probably in consequence of the 

 vaporisation of the free iodine from the solution in the tube. 



From these experiments it would appear that there is no 

 reason to believe, that water or its vapours confer volatility, 

 even in the slightest degree, upon those substances which alone 

 have their limits of vaporisation at temperatures above ordi- 

 nary occurrence, and that consequently natural evaporation 

 can produce no effects of this kind on the atmosphere. 



It would also appear that nitrate of ammonia, corrosive 

 sublimate, oxalic acid, and perhaps oxalate of ammonia, are 

 substances which evolve vapour at common temperatures. 



Royal Institution, Aug. 30, 1830. 



